1. FIELD OF THE INVENTION
The invention relates to apparatus for carrying out physical and/or chemical processes, in particular but not exclusively, a heat exchanger of the continuous type.
2. DESCRIPTION OF THE PRIOR ART
EP-A No. 132873 describes apparatus for carrying out physical and/or chemical processes which has a lower chamber and an upper chamber connected by a plurality of vertical riser tubes for passage of a first medium, e.g. first heat exchanging medium. Between the lower and upper chambers is an intermediate chamber for a second medium, e.g. second heat exchanging medium, which contacts the riser tubes. A fluidisable granular mass (i.e. a mass of separate particles) is present and in use is fluidised at least in the riser tubes by the flow of the first medium. One or more gravity tubes are provided for the return of the granular mass from the upper chamber to the lower chamber and extend to a lower level in the lower chamber than the riser tubes. A distribution plate for the first medium is located in the lower chamber at a level between the inlets of the riser tubes and the outlet of the gravity tube(s). The distribution plate has apertures for the passage of the first medium and the granular mass.
Various embodiments of the apparatus are disclosed in EP-A No. 132873, to all of which the present invention is applicable. For example, it is possible to fit one or more distribution devices for the first medium underneath in the lower chamber. In addition specially adapted shapes can be given to the bottom ends of the riser tubes,or the gravity tubes, depending on the required operational control.
The apparatus of EP-A No. 132873 is operated with a circulating granular mass fluidised at least in the riser tubes by the first medium. The granular mass rises up through the riser tubes, and falls again from the upper chamber into the lower chamber through the gravity tube or tubes. The importance of circulation flow of the mass via a gravity tube has already been described elsewhere for example in EP-A No. 132873. It is important that the granular mass returned to the lower chamber is delivered below the distribution plate, so that, together with the flow of the first medium, it is fed to the riser tubes evenly distributed by the distribution plate.
It is very important that during startup, after shutdown of the apparatus, the granular mass is all at the low level in the apparatus. This means that, when restarting the flow of the first medium, the granular mass can move freely to beneath the distribution plate. In various embodiments of the distribution plate for evenly distributing the first medium to the riser tubes, this does cause a problem, for example when the distribution plate is fitted with a larger number of relatively small holes to let the fluid and granular mass pass through, or the openings of the distribution plate are fitted with means for deflecting the direction of flow from the vertical direction.